The invention relates to a device for the shifting between an engaged and a released position of a multi-disk clutch for the locking of a transfer differential that can be driven by a driving machine, for the drive of two vehicle axles of a motor vehicle.
Such an arrangement has been contemplated in German Unexamined Published Patent Application (DE-OS No. 32 12 495). This device serves to adapt the locking torque of the multi-disk clutch fully automatically to various operating conditions of the vehicle as a function of parameters of the motor vehicle, such as the driving speed, the steering angle or the engine torque. For this purpose, the multi-disk clutch, by means of a hydraulic working pressure, is engaged against a release spring. The release spring is in the form of a plate spring which, in this case, acts as a power reservoir. In this case, the locking effects can be adjusted by the parameters by the control of the working pressure.
In contrast, the objective of the present invention is to allow the multi-disk clutch to operate over an extended operating time with a low energy expenditure in such a way that the working pressure, when the respective shifting signal occurs, always without delay has a predetermined continuously falling course over time.
This objective is achieved by providing a constant contact of the clutch disks in the opened condition ensured over the whole useful life of the clutch. Thus, the arrangement according to the invention can be used advantageously in those cases in which the closing of the multi-disk clutch is particularly critical with respect to time and a defined variation in time of the transferable engine torque is required. Because of the constant contact of the clutch disks, a minimal closing path is made possible.
In addition, the shifting point, i.e., that point in time at which the clutch disks are in complete contact with one another, does not depend on the spring characteristic of the spring means for the engaging of the multi-disk clutch and further does not depend on the installing condition of these means. Further, a settling or a wearing of the clutch disks cannot result in either a shifting of the shifting point or in a lengthening of the shifting process.
A further advantage is provided in that a separate shifting valve is not required which makes available a large flow cross-section until the shifting point is reached and subsequently makes available a reduced flow-off cross-section for the working pressure means.
Further, the shifting noise is low since less pressure medium must flow off because a venting path is lacking.
Finally, costly adjusting work with respect to the spring means for the engaging of the multi-disk clutch is not required.
These and other objects are made available by using a first spring for shifting the multi-disk clutch into engagement, providing an adjustable arrangement having a second spring adjustable with respect to a disk carrier for limiting the displacement of the first counterbearing on the disk carrier to only towards the pressure ring along the clutch axis, providing a second counterbearing fixed with respect to the disk carrier for supporting the pressure ring in the direction away from the first counterbearing along the clutch axis, and providing a hydraulic throttle in the return line which is connected with the working pressure chamber of the axial piston by the control valve to bring the clutch into the engaged position. The first spring is a plate spring applying force directly to the pressure ring which is connected to one end disk of the disk set which is opposite the disk engaged by the first counterbearing. The adjustment arrangement includes a threaded element for connecting the first counterbearing to the disk carrier in addition to the second spring. The threaded element is self-locking and the second spring may be a spiral spring. The disk carrier is immovably fixed on the transmission shaft central to the main axis of the transmission and the second counterbearing includes a retaining ring held in a circumferential groove of the transmission shaft. The second counterbearing may also include a plurality of stop screws in the disk carrier having an axis parallel to the multi-disk clutch axis. The stop screws are at the same distance to the clutch axis as the clutch release means that is applied to the pressure ring.
Other objects, advantages, and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.